The present invention relates in general to voice and data communications systems, and is more particularly directed to systems for providing integrated voice and data access to a T1 carrier data line terminating at the customer premises.
Providers of voice and data communications services frequently provide a connection to their customers' premises using a T1 circuit. The term “T1 circuit” is commonly used to identify a multiplexed 24 channel, 1.544 Mbps digital data circuit providing communications between two facilities or from a local service provider to a customer. “T1 ” refers to the transport of a DS1 formatted signal over a copper, fiber or wireless medium for deploying voice, data or video-conferencing services. The ‘T’ designation refers the bit rate and the copper transmission system and the ‘DS’ designation refers to the bit format and framing. However, many times the terms are used interchangeably. A single 64 kbps channel is called a DSO. The T1 rate of 1.544 Mbps for providing 24 channels of 64 kbps each is referred to as a “DS1.”
The T1 circuit is part of an extensive digital communications hierarchy that starts with 24 DSO's at 64 kbps each. These individual DSO's are used to provide voice or digital data to support point-to-point or network applications. By combining multiple DSO's, a high-speed interface can be provided to support a synchronous interface to a Local Area Network (LAN) router or voice PBX. For distances longer than one mile, a repeater is placed every mile to regenerate the signal.
As competition for providing dial tone and bandwidth to customers increases, communications service providers must find integrated access devices that allow cost-effective deployment of voice and data services at the customer's premises. Many T1 service customers will have a variety of different voice and data hardware devices and communications systems installed at the customer premises, each of which must share a connection to a single T1. Examples of customer premises communications devices that may require a concurrent interface to network T1 include:                analog telephone devices, requiring Foreign Exchange Office (FXO) and/or Foreign Exchange Subscriber (FXS) interfaces;        network routers, bridges, switches; and codecs (coders/decoders) used in audio broadcast and video conferencing systems; each having standard V.35 DTE (Data Terminal Equipment) interface connections;        Four wire DDS (Digital Data Service) devices, such as a CSU/DSU (Channel Service Unit/Data Service Unit) for connecting to a WAN (Wide Area Network);        ISDN (Integrated Services Digital network) devices; and        Fractional T1 communications.        
Conventional integrated T1 access devices may combine all of this functionality into a single unit that is not scaleable, meaning that the customer must often purchase a system having more functionality and more interface components into the device than the customer initially needs. Also, the requirements of the customer may change after the T1 integrated access unit is purchased. Because conventional integrated access devices are typically supplied with a hardware and interface configuration that is fixed internally, a change in customer needs may result in a costly internal re-configuration or equipment replacement decision by the customer. While a re-configuration takes place to add a new interface component, for example, the entire access unit must be disabled, thereby disrupting all of the customer communications systems that share the T1. In other words, it is difficult for the customer to “mix and match” the access device interfaces to the customer's different communications hardware as the customer's needs change after the access unit is purchase and initially configured. In fact, many conventional T1 integrated access devices cannot under any circumstances serve all of the customer's voice and data applications at the same time.
Another undesirable characteristic of conventional integrated access devices is the expense associated with the design of the different components that provide the interface to the different customer premises devices described above. Often, each of these interface components will be “smart”, having its own processor or other similar hardware and software to provide a high degree of ‘stand alone’ control of the operations of that interface component. The combined presence of this redundant processing power within each interface component of the integrated T1 access unit increases the total cost of purchase and ownership and may increase the complexity of device control and management.
In many applications where T1 access devices are installed at the customer premises, there is a need for a separate AC power supply to power the device as well as an auxiliary battery back-up system to protect the operation of critical communications devices that are connected to the T1 in the even of a power failure. There are a wide variety of conventional AC power supplies and back-up systems available for this purpose. A block diagram of a typical combination AC power supply and battery backup system 100 used in the prior are is shown in FIG. 13 A conventional rectification and power conditioning section 101 has two outputs as shown. The first output (output 1) is connected to an electronic system (such as a T1 access system) to provide power to the system during normal operation. The first output is also linked to a battery monitoring and back-up relay control circuit 102. The monitoring/control circuit 102 monitors the first output to determine if the voltage being supplied to the electronic system is within specified parameters for the electronic system and, if not, sends a signal to the normally-open relay circuit 103 to switch the battery 104 into the power circuit to the electronic system. The second output (output 2) is used to maintain a charge on the battery 104 and is connected to the battery 104 and opens the normally closed relay 106 when the battery electrical parameters deviate from normal.
There are several weaknesses in the typical prior art system 100 as illustrated in FIG. 13. Fist, because the rectification/conditioning section 101 must have two separate outputs, the complexity (e.g., parts count) of the section is increased which can add to the overall all expense of the system 100. Second, the separate charge limiting circuit 105 also increases the component count and power dissipations of the system 100. Third, the battery back-up function of the prior art system 100 is not entirely automatic because the battery 104 is not connected to the electronic system during normal operation. Rather, the monitoring and relay circuit 102 must be used to close the relay circuit 104 when an abnormal condition is detected at output 1.
Accordingly, there is a need for a low cost, easy to use system for allowing a small business customer to send and receive voice and data traffic over a single T1 terminating at the customer's premises. Preferably such a system will be scalable and easily re-configured to adapt to different communications needs of the customer. In addition, there is need for an improved and lower cost AC power supply and battery back-up system to power T1 interface devices as well as other communications equipment.